Turbo is an unreleased prototype that was developed for the Atari 2600 by Coleco, but was never commercially released. Like most of Coleco's Atari 2600 games, Turbo is an arcade port, based on the Sega arcade game of the same name. Until its discovery in 2006 by one of the game's original programmers, Turbo was considered one of the holy grails of Atari 2600 prototypes. This is due in part to the game being advertised by Coleco and included in their Atari 2600 catalogs, as well as an appearance by the game at the 1983 Consumer Electronics Show (CES).

Back in 2003 we orchestrated an April Fool's prank based around a fictional copy of Turbo being discovered in Connecticut. An image of a fake Turbo prototype PCB was fabricated, and homebrew author Thomas Jenztsch created a playable binary of the game that matched the screenshot of the game shown in the Turbo print advertisement. You can read the complete thread in our Atari 2600 Forum.

Fast forward three years to 2006 and one of our forum members noticed that someone had posted a video of a Turbo Prototype on Youtube. A discussion quickly began and this prototype was confirmed in short order to be legitimate. Turns out that one of the game's original programmers, Anthony Henderson, had discovered a Turbo prototype in his attic and posted a video of the game up on YouTube. The prototype was ultimately sold to an AtariAge member, who sent us the game so we could dump it as well as take pictures and scans of the prototype board and cartridge.

Although the game was close to being finished (we'd estimate it's around 80% complete), it was not released due to lead programmer Michael Green getting in a car accident during the game's development. While riding his bike, Michael Green was hit by a drunk driver and seriously injured. As a result, the game's deadline went by without the game being completed. By the time the project got back on track, the market had begun its infamous collapse and Coleco opted not to release the game. It's interesting to note that Coleco did produce at least a limited run of cartridge labels for the game, as you can see here.

You can read a complete review of this unreleased prototype (including a thorough description of the gameplay) over at AtariProtos.com.